Field of the Invention
The present invention relates to a vertical machining center.
Discussion of the Background
Vertical machining centers including a tilting rotary table are capable of five-axis machining on a workpiece placed on the table, and thus capable of machining a workpiece of a complicated shape. The vertical machining centers are capable of, at one set-up, machining all the surfaces of the workpiece excluding the surface to be mounted to the table, and thus ensure high machining efficiency.
A tilting shaft for rotating to tilt the rotary table has three types of support structure, such as a double-support single-drive type, a double-support double-drive type, and a single-support single-drive type.
The tilting shaft is disposed in a right-left direction as seen from the front of the machine (that is, A axis direction) or in a front-rear direction of the machine (that is, B axis direction).
In a machine with the tilting shaft disposed in the A axis direction, when the table is tilted toward the other side of the front surface of the machine, an operator standing in front of the machine has difficulty in visually checking the portion that is being machined. The machine, however, can employ a tilting shaft support structure of any type.
Meanwhile, in a machine with the tilting shaft disposed in the B axis direction, when the table is tilted toward the left or the right, the operator standing in front of the machine can easily visually check the portion that is being machined. Unfortunately, in the tilting shaft support structure of the double-support type, the tilting shaft support member obstructs the operator working in front of the machine.
In view of workability and visibility for the operator in front of the machine, Japanese Unexamined Patent Application Publication No. 2007-296613 discloses an exemplary machine tool wherein a tilting shaft of the single-support single-drive type is disposed in the B axis direction, in an attempt to maintain high accuracy.